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Photoinduced charge-separation in DNA.

Kiyohiko Kawai1, Tetsuro Majima

  • 1The Institute of Scientific and Industrial Research, Osaka University, Mihogaoka 8-1, Ibaraki, Osaka, 567-0047, Japan, kiyohiko@sanken.osaka-u.ac.jp.

Topics in Current Chemistry
|March 1, 2014
PubMed
Summary

DNA charge-separation dynamics were studied using photosensitizers. Long-lived charge-separated states (τ > 0.1 μs) were formed via photoinduced charge transfer, with mechanisms varying based on DNA base pairs and photosensitizer type.

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Area of Science:

  • Photochemistry
  • Molecular Biophysics
  • DNA Nanotechnology

Background:

  • Understanding charge dynamics in DNA is crucial for developing DNA-based electronic devices.
  • Site-specific modification of DNA with photosensitizers allows for controlled investigation of charge transfer processes.

Purpose of the Study:

  • To investigate the mechanisms of charge-separation and charge-recombination dynamics in DNA.
  • To identify conditions favoring the formation of long-lived charge-separated states in DNA.
  • To explore the role of DNA base-pair composition and photosensitizer properties in charge transfer.

Main Methods:

  • Synthesis of DNA site-specifically modified with photosensitizers (naphthalimide, naphthaldiimide, anthraquinone).
  • Laser flash photolysis technique to measure quantum yields (Φ) and lifetimes (τ) of charge-separated states.
  • Site-specific modification of DNA with 5-bromouracil to probe charge transfer pathways.

Main Results:

  • Long-lived charge-separated states (τ > 0.1 μs) were successfully generated in DNA.
  • Charge-separation mechanisms were elucidated, involving photoinduced charge-injection into adenine (A) and hole transfer between adenine-thymine (A-T) base pairs.
  • Replacing thymine with 5-bromouracil altered charge-separation pathways.
  • Common fluorescent dyes (TAMRA, Alexa 532, ATTO 655) also induced charge-separation, primarily involving guanine-cytosine (G-C) base pairs.

Conclusions:

  • Charge-separation in DNA is a general phenomenon facilitated by photosensitizers and influenced by DNA base composition.
  • The mechanism of charge-separation depends on the photosensitizer's electronic properties and its interaction with specific DNA base pairs.
  • Long-lived charge-separated states can be generated using various photosensitizers, suggesting potential for DNA-based charge transport applications.